Product Reviews

Product Reviews

On this page you will find occasional reviews of "MakerStuff" that has come into the hands to one or more T-Exchange members and, on which they wish to comment for the benefit of other members. We will try to provide a link to each supplier where you can get fuller info.

Long-range Remote-control over WiMo

Sometimes the challenged maker seeking remote control may find that WiFi is a a NoGo. Time to try WiMo. Yes, that's right, Wires-More. In this case, cable in the form of UTP (unshielded twisted pair) or STP (shielded twisted pair), better known as Ethernet or Network cable. In the case of an electrically noisy environment (like a factory) or a solid stone building (like Nelson's Tower in Forres) WiFi may not be the best choice. You may not even want a WiFi enabled computer with a load of hand-crafted software at each end. A good solid serial link may do the job. Do you remember RS232 on early computers? Well, it's time to look at RS485.

RS485 is an international standard for balanced two-way transmission of digital data with a high degree of integrity over cable disstances up to 1km or more. If you want more details see Wikipaedia here. However, if you just want to get wiring, you should get familiar with theMAX485 module.

This is available from Hobby Components for the very useful sum of £1.99 each. With a pair of these you will soon be up and running. If you want two way data exchange, the modules have a directional hand-shaking arrangement that can be controlled directly by the GPIO pins on your Raspberry Pi or Ardiuno.

For my Nelson's Tower camera project, I am sending data from an optical coding wheel on the ground floor, via four MAX485 modules and a UTP cable, to a stepping motor circuit on the viewing deck for camera motion control. The pulses from the optical sensor are only 10 microseconds long and needed to be stretched to 1 millisecond to give a clean signal at the receiver. This was done with a 555 timer. The modules then worked perfectly on cable tests of 130m. I will post more information about the project later. In the meanwhile, here is a picture of the transmission end of the setup. (Note the custom 3D printed parts and stripboard wiring.)

Bill Graham 270416

Robots

The CIC Taiwan Robot Arm - Sold in the UK by Maplin

This is a very popular robot arm kit in the UK and has been a big hit for Christmas and birthdays with emerging teenagers and their mentors (dads? mums?). There are lots of reviews of this kit on the Internet so if you have one or are hoping for one then do read these, generally helpful, reviews. The main criticism has been about the lack of position feedback as all movements are open loop and errors accumulate. However, the user interface allows a 'programer' to construct interesting programs and save them for reuse. It is a well made, comprehensive kit and illustrates many principles of how a factory robot works incluing the importance of accurate positioning. The kit is educational and very good value.

My review is a bit more detailed than most that can be found on Web shops and is supplementary to them. It includes a procedure for producing program files by typing the code rather than using the "learning by driving" method. This enables quicker construction of long motion sequences, e.g. picking and repositioning several objects. Click here to download the review as a PDF file.

Review by Bill Graham 060115

Test Equipment

Tenma Model 72-7770 Multimeter (Farnell)

This is a palm-sized Digital multimeter, supplied with an elastomeric body-guard, back-light, 50Hz, 3V square wave signal and a pair of probes. This is in addition to a decent specification of 4 digit display, 2mA-10A, 200mV-500V DC, 200-50V AC and 200 Ohm-200MOhm.
This instrument is available from Farnell - Element 14 for £8.12 +VAT at 23rd May 2014.

T-Exchange members commented:

"Amazing Value. Very useful instrument"

"Very handy. Worked well for testing old oscilliscope PSU"

"Needing to unscrew tiny screws to replace batteries is not so great. Slide-off covers are easier."

"Full (good) English manual is very unusual for the price"

" On sensitive settings the display can wiggle and be a bit slow to settle"

"The back-lit display is great for use in dark corners".

PicoScope 2204A - Pocket Digital Oscilloscope

A few weeks ago the poor old Phillips 'scope died. It was 35 years old and at least twice as heavy. Since we need to carry our kit to and from our makerspace meeting room, something portable was called for.

The new PicoScope 2204A was quickly identified as in a suitably small price bracket and obtained from Farnell. The first job was to check out the pulses from the optical encoder disc shown in the upper left above.

The DC - 200 pulses/second, were a bit of a laugh to the 10MHz PicoScope but this is the kind of speeds we need to look at in many of our Makerspace projects. The image in the top right shows you the encoder's neat pulse-form and gives you some idea of the comprehensive interface provided by the included PicoScope 6 software (with free upgrades).

The interface has none of the rotary knobs of a conventional oscilloscope but uses drop-down menus that may be a bit baffling to start with. However, a very extensive help manual can be opened at any moment and provides instant answers. See the bottom left picture.

The bottom right picture illustrates that the PicoScope really is a hand-held device that, with a notebook or laptop PC, puts a powerfull, fully-portable oscilloscope in your hands. Not only are there two DC – 10MHz inputs provided but also a signal generator output. This connects to the third BNC conector labelled AWG for Arbitrary Waveform Generator. You can define your own waveform or use a number of standard shapes built in. Very useful.

You can get fuller details from the Farnell – Element 14 web site at:www.farnell.com
where the instrument is currently on offer at £119 plus VAT.

The old Phillips oscilloscope cost several thousands of pounds. That's progress, that is.